Polyformals based on Bisphenol A were first reported by Barclay U.S. Pat. No. 3,069,386. They were made by reaction of the anhydrous disodium salt of Bisphenol A with one equivalent of bromochloromethane in dimethyl sulfoxide. More recently, Hay, et al, in a recent presentation entitled "Synthesis of New Aromatic Polyformals", at the 1982 Fall ACS Meeting in Kansas City, Mo., addressed their manufacture.
German Often. No. 2,738,962, published May 11, 1978, based on U.S. application Ser. No. 739,562, filed Nov. 8, 1976, describes the manufacture of aromatic polyformal resins in which the units have the structure--OROCH.sub.2 --and wherein R is an arylene of 6 to 30 carbon atoms and the resin has an intrinsic viscosity of about 0.3 dl/g, measured in chloroform at 25.degree. C. They are prepared specifically from Bisphenol A, an excess of methylene halides, and an alkali metal hydroxide.
German Often. No. 2,819,582, published Sept. 27, 1979, based on U.S. application Ser. No. 889,393, filed Mar. 23, 1978, describes flexible, film-forming polyformals having the repeating structure: ##STR3## which are manufactured by the reaction of one mole of Bisphenol A and at least a stoichiometrically equivalent amount of methylene halide in the presence of at least a stoichiometrically equivalent amount of an alkali metal hydroxide and a phase transition catalyst, with or without a dipolar aprotic solvent. This patent publication appears to correspond to the Hay et al ACS publication.
One of the disadvantages with polyformals derived from 2,2-bis-(4-hydroxyphenyl)propane (Bisphenol A) and a methylene halide is their immiscibility with styrenic polymers, vinyl chloride containing polymers and the like. Polyformals miscible and compatible with styrenic polymers, vinyl chloride containing polymers and the like would be highly desirable for increasing heat distortion temperatures and therefore allowing for a broader range of end-use applications.
U.S. Pat. No. 4,374,974 describes polyformals prepared from a mixture containing a methylene halide, a bisphenol, an alkali metal hydroxide and a phase transfer catalyst or a dipolar aprotic solvent. Example 16 shows the preparation of a polyformal derived from bis-(3,5-dimethyl-4-hydroxyphenyl)sulfone (TMBS) and methylene bromide, which polyformal consists of chemically combined units of the formula ##STR4## The polyformal is stated to be highly insoluble in non-polar organic solvents.
One of the problems with polyformals derived from bis-(3-5-dimethyl-4-hydroxyphenyl)sulfone (TMBS) and a methylene halide is their instability at required high processing temperatures. Another problem with polyformals derived from bis-(3,5-dimethyl-4-hydroxyphenyl)sulfone (TMBS) and a methylene halide is brittleness of molded articles prepared therefrom. Polyformals having good processability at high temperatures and providing improved toughness and ductility to molded articles prepared therefrom would be highly desirable.